Tuesday, February 1, 2011

Polled Goats

Polled goats are goats who are born without horns. It is a genetic and therefore heritable trait. We love our polled goats because we HATE to have to burn the heads on tiny baby kids. We have chosen to select for the polled trait whenever possible.

So, if it makes it so you do not have to disbud kids, why doesn't everyone breed polled? Because there is a lot of misinformation and old wives tales out there that have given polled goats a bad reputation. There is the fear that if you breed a polled goat to a polled goat, the resulting goats are all sterile. According to the published information available, this is just not true. I have tried to summarize what i have found below. I will try to add references in the future, as time allows :)

The first peice of information to understand is that there are two gene sites that control two traits.  One controls polled versus horned. The other controls the intersex gene. These two sites are linked together (they are located very close together on chromosome #1, so they always "go together." In other words, if the goat has the polled gene they also have the "potential" to be a female hermaphrodite (intersex).
The other 3 pieces of important information:
#1 Polled is dominant over horned (so you can get a polled goat if that gene site is (+/+) or (+/-),

#2 The gene that causes hermaphrodites (intersex) is a recessive, it only shows up with a homozygous recessive (ie, two genes, one
from each parent, that are the recessive (-/-). If it is heterozygous (+/-) or homozygous dominant (+/+), then they are
normal polled goats.

#3 Only females end up hermaphrodites. 

So, if you have a polled goat that you know was produced from a polled and horned pairing, you know it is heterozygous (-/+) for the polled gene. For the intersex gene, if it is not a Hermie, you know it is not (-/-) but you don't know if it is (-/+) or (+/+)....so if you were to breed that animal to another polled animal, the chances of getting a male is 50/50 and they will never be a hermie. A female has either a 50/50 if one parent is (+/+) and the other is (+/-) or 1 in 4 if both parents are (-/-).
So worst case scenario is about 1 in 8 chance of getting a hermie. We have never actually had one yet, but when we do, we will just treat like a wether, so no big deal.
It is well worth that "risk" to not have to disbud kids all the time.

OK, that is the goat genetics lesson for ya'all. Hope someone finds it useful.

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